cut legacy backcompat alias folly::io::hasCodec

Summary: All uses have been migrated so the unused alias may now be removed.

Reviewed By: Gownta

Differential Revision: D68616601

fbshipit-source-id: c31e03245c0c9d5d0cf7bca78d331019a3709efa

Author: yfeldblum

folly/compression/Compression.h

@@ -544,5 +544,4 @@ namespace folly::io {
 using folly::compression::Codec;
 using folly::compression::CodecType;
 using folly::compression::getCodec;
-using folly::compression::hasCodec;
 } // namespace folly::io